The present invention relates to an apparatus for transferring mechanical movements representing measured quantities.
In industrial measuring and control technology apparatuses are frequently found within which mechanical quantities, such as a path or force, are represented by electrical quantities, such as voltage, current, resistance or conversely electrical quantities are represented by mechanical quantities. Arrangements of this type which frequently occur are e.g. electropneumatic IP or PI converters (current/pressure or pressure/current converters), electropneumatic valve positioners and the like. The electrical components for converting path quantities into electric quantities are often DMF strips, Hall generators or differential transformers. In the case where electric quantities have to be converted into a force, use is frequently made of moving coils or electromagnets, preference being given to the moving coil because it produces a force precisely proportional to the current flowing through it.
Apparatuses, instruments and equipment of the aforementioned type are frequently used in operating rooms, in which unintentionally explosive gaseous mixtures can form. Thus, the plant operator requires measures to ensure that the initial energy necessary for igniting the explosive ambient atmosphere can never form. One possible solution for this problem involves constructing the particular apparatus with maximum security, so that through the appropriate configuration of the current paths and the choice of the working voltage, it is ensured that the initial energy necessary for igniting the mixture, e.g. in the form of sparks or high surface temperatures cannot form at any point on the electrical components, such as on the moving coil or the like. Another way of achieving the desired effect is either to provide an encapsulation with protective scavenging or a pressure-tight encapsulation. Encapsulated constructions have the advantage that higher electrical energies can be used, so that it is possible to a certain extent to reduce the space requirements for the electrical components compared with the aforementioned fail-safe construction with the appropriate configuration of the current paths and the like. However, both the fail-safe construction and that with pressure encapsulation suffer from the disadvantage of bulkiness or a significant weight of the correspondingly constructed apparatus. Naturally the aforementioned problem more particularly occurs in the above-stressed explosion-proof apparatus, but fundamentally also occurs in the case of apparatuses of the more general type, where it is a question of permitting the transfer of mechanical motions from explosion-proof rooms, within which ignition energy can form in some other way than electrically, e.g. thermally or by sparking.
DE-AS No. 10 93 900 already discloses an apparatus of the aforementioned type in which there is a force or motion transmission by a longitudinally displaceable rod between the electric assembly and the mechanical assembly. This rod must be carefully adjusted within the opening or passage, so that a contact-free deflection thereof is possible. This leads to considerable mounting problems.